Pneumonia: Causes, Symptoms & Treatment

A guide to pneumonia - a lung infection that inflames the air sacs, its causes, symptoms, and treatment

10 min readLast updated: 2026-02-17

Quick Facts

Incidence
~1.5 million ER visits/year in the US
Mortality
Leading infectious cause of death in children worldwide
At-Risk Groups
Children under 5, adults over 65, immunocompromised

What Is Pneumonia?

Pneumonia is an infection that inflames the air sacs (alveoli) in one or both lungs. The air sacs may fill with fluid or pus, causing cough with phlegm, fever, chills, and difficulty breathing. Pneumonia can range from mild to life-threatening, and is most serious for infants, young children, people over 65, and those with weakened immune systems or chronic health conditions.

Types of Pneumonia
Pneumonia is classified by where it was acquired and what caused it. Community-acquired pneumonia (CAP) develops outside of hospitals. Hospital-acquired pneumonia (HAP) develops during hospitalization. The most common bacterial cause is Streptococcus pneumoniae. Viral causes include influenza, RSV, and SARS-CoV-2. Atypical bacteria (Mycoplasma, Chlamydophila, Legionella) cause "walking pneumonia."

Symptoms

  • Cough, often producing green, yellow, or bloody mucus
  • Fever, sweating, and shaking chills
  • Shortness of breath
  • Chest pain that worsens with breathing or coughing (pleuritic pain)
  • Fatigue and malaise
  • Nausea, vomiting, or diarrhea
  • Confusion (especially in older adults)
  • Lower-than-normal body temperature (in elderly or immunocompromised)

Treatment

Community-acquired pneumonia in otherwise healthy outpatients:

  • Amoxicillin, or a macrolide (azithromycin, doxycycline) if penicillin-allergic

Outpatients with comorbidities:

  • Amoxicillin/clavulanate or cephalosporin PLUS macrolide or doxycycline
  • OR respiratory fluoroquinolone (levofloxacin, moxifloxacin) alone

Hospitalized patients:

  • IV antibiotics (beta-lactam plus macrolide, or respiratory fluoroquinolone)
  • Oxygen therapy as needed
  • IV fluids
  • Monitoring and supportive care

Viral pneumonia:

  • Influenza: Oseltamivir (Tamiflu) within 48 hours of symptom onset
  • COVID-19: Antiviral therapy, steroids, and other treatments per current guidelines
  • Supportive care: Rest, fluids, fever management

Self-care for mild pneumonia:

  • Rest and adequate sleep
  • Plenty of fluids
  • Take all prescribed antibiotics as directed (complete the full course)
  • Fever-reducing medications as needed
  • Follow up with your doctor if symptoms are not improving within 48-72 hours
Warning
Seek emergency care if you experience severe difficulty breathing, chest pain, confusion or altered mental status, persistent high fever above 102°F (39°C), or if you are over 65 or have chronic health conditions and develop pneumonia symptoms. Pneumonia can rapidly become life-threatening.

Prevention

  • Vaccination: Pneumococcal vaccines (PCV20 or PCV15 + PPSV23) for adults 65+ and high-risk groups; annual influenza and COVID-19 vaccines
  • Good hand hygiene
  • Don't smoke (smoking damages lung defenses)
  • Manage chronic conditions
  • Get adequate rest and nutrition
Clinical Note
The CURB-65 score (Confusion, Urea >7 mmol/L, Respiratory rate >=30, Blood pressure systolic <90 or diastolic <=60, age >=65) helps determine whether a patient with pneumonia can be treated as an outpatient or requires hospitalization. A score of 0-1 suggests outpatient treatment; 2 consider hospitalization; 3+ requires hospitalization, possibly ICU.

When to See a Doctor

See a doctor if you have persistent cough with fever, difficulty breathing, or chest pain. Seek immediate care if symptoms are severe, if you are over 65, if you have chronic lung disease or a weakened immune system, or if a young child develops symptoms.

Sources

  1. [1]Metlay JP, Waterer GW, Long AC, et al.. "Diagnosis and Treatment of Adults with Community-acquired Pneumonia: ATS/IDSA Guideline." American Journal of Respiratory and Critical Care Medicine, 2019.
  2. [2]Wunderink RG, Waterer G. "Community-Acquired Pneumonia." New England Journal of Medicine, 2014.

Medically reviewed by

Medical Review Team, Pulmonology

Last updated: 2026-02-17Sources: 2

The content on Medical Atlas is for informational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider.

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